A NEBULIZER SYSTEM FOR HIGHLY REPRODUCIBLE AEROSOL DELIVERY

The output characteristics of current nebulizer systems are influenced by factors such as inspiratory flow, temperature and relative humidit y of the ambient air as well as surface tension of the nebulizing solu tions. Due to the resulting alteration of droplet characteristics the delivery of aerosolized drugs is variable. A nebulizer system, the PAR I IS-2, has been designed for the delivery of aerosolized potent drugs . It is characterized by a highly consistent aerosol output acid a hig h proportion of droplet mass in the respirable range. Laboratory testi ng was performed with a Malvern Particle Sizer and by measurement of t otal and effective output rates. Preconditioned air was supplied to th e system in order to simulate different inspiratory flows (steady stat e) at varying ambient conditions. There was only a small effect on dro plet sizes (MMD 3.0 to 3.6 mu m) over the investigated range of inspir atory flow, ambient conditions and drug solutions. Total and effective output rates of the nebulizer were found to be linearly proportional between 5 and 20 1/min inspiratory now thereby compensating for the di lution of aerosol by entrained air. Total output, at a relative humidi ty between 20% and 80% and at fixed inspiratory now, varied only by +/ -6% with respect to 50% relative humidity (r.h.). The proportion of th e dose delivered from the system ranged from 28% to 67% for an initial fill volume between 0.5 and 3 ml, respectively. Thus, for standardize d breathing and by using the manual interrupter for on-command therapy , a highly effective delivery and deposition of therapeutic aerosols i n the lungs may be achieved with the PARI IS-2 nebulizer system. Due t o the small droplet sizes (80% of the mass below 5 mu m), side effects caused by aerosol deposition in the mouth and oropharynx are expected to be reduced to a minimum.